Laser-Assisted in Situ Keratomileusis (LASIK) is a well-known laser eye surgery for correcting defects of vision including myopia (commonly referred to as “short-sighted”), hyperopia (commonly referred to as “far-sighted”), and astigmatism.
LASIK is performed by first forming a thin hinged flap out of the top of the cornea. The hinged flap is then folded back and the shape of the exposed cornea is changed by using an excimer laser to ablate away material. After ablating away the required material, the flap is folded back into place. The flap typically heals back into place in a few days.
The thin flap may be formed by cutting with a microkeratome or by using a femtosecond laser to photodisrupt a thin layer of the cornea, as described in more detail below.
Reshaping of the cornea is a particularly effective way of correcting vision defects as, in the typical human eye, the refractive power of the cornea accounts for approximately two-thirds of the total refractive power of the eye. In addition, the procedure takes about fifteen minutes. Because of the speed, efficacy and simplicity, LASIK has become a very popular procedure, with over 24.6 million procedures already performed, and over 6 million procedures being performed annually at a cost of over $1000.00 per procedure.
Forming the flap remains the least predictable part of the LASIK procedure and currently limits the degree to which procedures can be customized for individual correction of vision defects. Moreover, imperfect healing of the flap is a factor in about 5% of the procedures and may lead to a variety of problems including, but not limited to flap striae, epithelial ingrowths beneath the flap, diffuse lamellar keratitis, and flap tears.
A highly desirable improvement to the important field of the correction of vision by reshaping the cornea would, therefore, be to eliminate the need for creating the flap in LASIK type procedures.